1. Field of the Invention
The invention relates to louvered venetian blinds, particularly vertical venetian blinds, having several types of carriers which may be shifted along a headrail and through which carriers a drive shaft passes, which drive shaft has at least one helical groove. The carriers may include louver carriers with one louver carrier for each louver as well as pull carriers for traversing axially of the drive shaft and arranging the louver carriers either evenly distributed over the face of the window or arranged in packs of louvers at the sides.
The types of carriers may also include support carriers for preventing the sagging of the drive shaft in those areas of the shaft where there is no louver carrier or pull carrier. Preferably, the support carriers may be individually retained at predetermined points along the headrail by use of stops provided on the rail.
2. Prior Art
In one known type of venetian blind, the louvers can be turned (without axial traverse or transport) about their vertical axes through an angle of more than 150.degree. by means of the drive shaft. When it is desired to use support carriers in such a type of venetian blind, which carriers are transported by means of the drive shaft, great disadvantages can occur in practice if the support carrier is permitted to traverse axially of the drive shaft during the time that the drive shaft is rotating the louvers about their vertical axes. If this occurs, the support carrier may run up against the first louver carrier or a pull carrier, thus applying an axial transport force against the first louver carrier or pull carrier which is undesired. In such blinds, the support carriers are only connected frictionally to the drive shaft. However, the transport action exerted in the axial direction of the shaft upon the support carrier is, nevertheless, of such a magnitude that undesired transport of the support carrier (and ultimately of the next adjacent louver carrier or pull carrier) can take place.